The Effects Of Age On Drop Landing Tibial Accelerations In U.S. Army Trainees

Landing activities are one of the most common causes of the high rates of musculoskeletal injury in Army trainees during Basic Combat Training (BCT). Injury rates have been shown to be highest in trainees 25 years or older. Impact forces during drop landings are associated with injury. As peak tibial accelerations (TAs) can be a good surrogate of impact forces, age differences in peak TAs during drop landings may provide insight into the causes of higher injury rates in older trainees. PURPOSE: To evaluate age-related differences in peak TAs among Army trainees at the beginning of BCT METHODS: 522 trainees (321 men, 201 women) participated in data collections during the first week of BCT. Participants were outfitted with inertial measurement units (IMUs) attached to the bilateral distal antero-medial tibia, just above the medial malleoli. Participants were given three practice trials before performing three successful trials of each task. Tasks included double- and single-leg (right/left) drop landings from 18” and 12” boxes, respectively. Peak vertical and resultant TAs during landings for the dominant leg only were extracted and averaged across trials. Participants were grouped by age as young (≤19 yrs), middle (20-24 yrs), or older (≥25 yrs). ANOVAs were used to compare mean TAs across age groups and sexes. RESULTS: There were no significant main effects of age (Table 1) or interaction effects of age and sex (p = 0.37 - 0.66) for either task. CONCLUSION: These results demonstrate that peak TAs, or impacts, are not different across ages in Army trainees. This suggests that landing impacts may not be the primary factor in the higher injury rates seen in older trainees during BCT. Other factors related to older age may be more predominant causes of higher injury rates. Supported by US DoD award W81XWH-20-C-0123 P0001. The opinions/assertions in this manuscript are the private views of the authors and are not to be construed as official policy or reflecting the views of the US Army.